Uh.. does it even work?!

I am using this on a site with a lot of images.. without thinking. Today I tried this on a small site with just a few images. One of them was a png that was 750kb.. way too big. It smushed it. It said it was optimized.. size was the same.
I just threw the file in tinypng and it made it 200kb. So.. what’s Smush’s problem?? It’s not even working!